Do you really have to refrigerate sake?

I've got a bottle of 15%ABV Californian Sho Chiku Bai, and it says "refrigerate after opening".

I have a bottle of Japanese sake, which it never occurred to me to keep in the fridge, and it's still lovely months after opening. Similarly sherry, which can also be 15% ABV, I never keep in the fridge.

So is this really necessarily, or is it an American 'thing' to keep sake in the fridge?